That simple fact must be restated to counter environmentalists' baseless
allegations that the accumulation of man-made carbon dioxide, produced by
cars, power plants and other human activities, is causing dangerous global
warming.

Indeed, far from being a poisonous gas that will wreak havoc on the planet's
ecosystem, carbon dioxide is arguably the Earth's best friend in that trees,
wheat, peanuts, flowers, cotton and numerous other plants significantly
benefit from increased levels of atmospheric carbon dioxide.

Dr. Craig Idso of the Center for the Study of Carbon Dioxide and Global
Change, one of the nation's leading carbon dioxide research centers, examined
records of atmospheric carbon dioxide concentrations and air temperature
over the last 250,000 years. There were three dramatic episodes of global
warming that occurred at the end of the last three ice ages. Interestingly,
temperatures started to rise during those warming periods well before the
atmospheric carbon dioxide started to increase. In fact, the carbon dioxide
levels did not begin to rise until 400 to 1,000 years after the planet began
to warm. Concludes Dr. Idso, "Clearly, there is no way that these real-world
observations can be construed to even hint at the possibility that a significant
increase in atmospheric carbon dioxide will necessarily lead to any global
warming."1

On the other hand, scientists have lots of evidence demonstrating that
increased carbon dioxide levels leads to healthier plants. A team of scientists
in Nevada conducted a five-year experiment in which they grew one group
of ponderosa pine trees at the current carbon dioxide atmospheric level
of about 360 parts per million (ppm) and another group of pines at 700 ppm.
The doubled carbon dioxide level increased tree height by 43 percent and
diameter by 24 percent. Similarly, a team of scientists from Virginia Tech
University reported that growing loblolly pine trees in a greenhouse with
a carbon dioxide concentration of 700 ppm increased average tree height
9 percent, diameter by 7 percent, needle biomass by 16 percent and root
biomass by 33 percent.2

Increased atmospheric carbon dioxide doesn't just make a plant bigger.
Carbon dioxide also makes plants more resistant to extreme weather conditions.
In a study discussed in the journal Plant Ecology, a team of scientists
subjected the Mojave Desert evergreen shrub to three different concentrations
of carbon dioxide - the current level of 360 ppm and at 550 ppm and 700
ppm. The plants, which were being grown in simulated drought conditions,
responded more favorably in the carbon dioxide-rich environments. Photosynthetic
activity doubled in the 550 ppm environment and tripled at 700 ppm. Increased
photosynthetic activity enables plants to withstand drought better.3

Likewise, a team of biologists grew seedlings of three yucca plants in
cooler greenhouse environments at the 360 ppm and 700 ppm concentrations.
The yucca plants exposed to the enhanced carbon dioxide concentration showed
a greater resistance to the colder temperatures. Dr. Robert Balling, a climatologist
at Arizona State University, notes that by making plants healthier and more
resistant to extreme weather conditions, higher levels of atmospheric carbon
dioxide expands the habitat of many plants, improves rangeland in semi-arid
areas and enhances agricultural productivity in arid areas.4

Another benefit of enhanced atmospheric carbon dioxide is that it helps
the tropical rainforests. Scientists from Venezuela and the United Kingdom
grew several species of tropical trees and other plants in greenhouse conditions
at carbon dioxide concentrations double the current level. The plants responded
favorably, showing an increase in photosynthetic activity. The scientists
concluded that, "In a future atmosphere with a higher carbon dioxide
concentration, these species should be able to show a higher productivity
than today."5

Another team of British and New Zealand researchers grew tropical trees
for 119 days at elevated levels of atmospheric carbon dioxide. They found
that the enriched carbon dioxide environment stimulated the trees' root
growth by 23 percent. Expanded root systems help tropical trees by increasing
their ability to absorb water and nutrients.6

Bigger trees, increased resistance to bad weather, improved agricultural
productivity and a boon to rainforests are just some of the many benefits
that carbon dioxide bestows on the environment. With little evidence that
carbon dioxide triggers dangerous global warming but lots of evidence showing
how carbon dioxide helps the environment, environmentalists should be extolling
the virtues of this benign greenhouse gas.